The present invention relates to a wheel assembly of the type comprising at least two contact members which are rotatable along a contact surface and equally spaced on a carrier which is movably connected to a frame, e.g. a portion of a wagon body, a vehicle chassis, a container or a conveyor for the purpose of moving the frame relatively the contact surface.
The problem solved by prior art assemblies of the type above defined has been to make it possible to pass upwards or downwards on stair steps. In other words, the prior art devices have been designed to "climb" up or down the stairs and, more specifically by rotation of the carrier relative to the frame in such a way that two of the wheels mounted on the carrier are in simultaneous contact with the horizontal surfaces of at least two of the stair steps. The technical problem solved by such devices was consequently a conversion of the discontinuous, jerky movement into a smoother and more continuous movement, the ideal aimed for being a trajectory parallel to the tangent through the outer corners of the steps.